CVE-2026-55604 @arikusi/deepseek-mcp-server has an Authorization Bypass Through User-Controlled Key
Attackers can hijack user sessions by guessing session IDs to read and modify conversation context in DeepSeek MCP Server.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-55604?
CVE-2026-55604 is a high-severity authentication bypass vulnerability in arikusi deepseek-mcp-server, published on 9 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
DeepSeek MCP Server is an MCP server for DeepSeek V4. Starting in version 1.4.2 and prior to version 1.7.0, the process-global `SessionStore` accepts caller-supplied `session_id` values without binding them to any authenticated principal or transport session. An attacker can enumerate active session IDs via `deepseek_sessions`, then reuse a victim-controlled `session_id` in `deepseek_chat` to retrieve and continue the victim's conversation context. Version 1.7.0 contains a patch.
Weakness: CWE-639
Which versions are affected by CVE-2026-55604?
2 open source packages ship an affected version, including @arikusi/deepseek-mcp-server.
| Package | Affected | Fixed in |
|---|---|---|
@arikusi/deepseek-mcp-server npm | From 1.4.2 | 1.7.0 |
@arikusi/deepseek-mcp-server npm | From 1.4.2 | 1.7.0 |
How do I fix CVE-2026-55604?
Upgrade @arikusi/deepseek-mcp-server to 1.7.0 or later.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-55604 being exploited?
There is no known exploitation of CVE-2026-55604 in the wild and no public exploit code.
Sources
Also known as GHSA-fh3r-g96v-f578.